1. Field of the Invention
The present invention relates to a soundproof cover which is disposed to a noise source, such as an intake manifold of an automobile, and which can inhibit noises by insulating sounds being generated by the noise source.
2. Description of the Related Art
Automobiles comprise many vibrating component members in which engines are principal one of such component members. To reduce the noises, which are generated by their vibrations, is one of the assignments to automobile engineers. Hence, it has been carried out disposing soundproof covers, which cover the noise sources. For example, in Japanese Unexamined Patent Publication (KOKAI) No. 10-205,352, there is disclosed a soundproof cover, which is constituted by a hard sound insulation layer and a sound absorption layer. The hard sound insulation layer is formed of a resin or steel plate. The sound absorption layer is laminated on one of opposite surfaces of the sound insulation layer which faces a noise source, and is formed of a polymer foamed substance. In this soundproof cover, the sound insulation layer insulates the sounds, which come from the noise source, and the sound absorption layer absorbs the sounds, which come from the noise source.
Namely, the sound waves, which are generated by the noise source, are absorbed by the sound absorption layer to a certain extent when they pass through the sound absorption layer. The rest of the sound waves, which are not absorbed, arrive at the sound insulation layer. Since it is difficult for the sound waves to pass through the hard sound insulation layer, the sound waves are reflected at the sound insulation layer and pass through the sound absorption layer again. Therefore, the sound waves are reflected repeatedly between the noise source and the sound insulation layer so that they are absorbed every time they pass through the sound absorption layer. Accordingly, it is possible to effectively carry out soundproofing.
Moreover, in Japanese Unexamined Patent Publication (KOKAI) No. 9-134,179, there is disclosed another soundproof cover. In this soundproof cover, a sound absorption layer is formed so as to conform to a superficial configuration of a noise source. Moreover, the sound absorption layer is disposed so as to adhere to the noise source. When the sound absorption layer is thus adhered to the noise source, no clearance arises between the soundproof cover and the noise source. Consequently, it is possible to inhibit the noises from leaking through such a clearance.
However, since the sound insulation layer is usually formed as a hard plate shape, there is a drawback in that the sound insulation layer itself makes a noise source when it vibrates. Hence, it has been carried out thickening the sound absorption layer so as to inhibit the sound waves from reaching the sound insulation layer and vibrating the sound insulation layer. Moreover, it has also been carried out fastening the sound insulation layer to the noise source by way of a vibration insulation component member, such as a rubber mount, a grommet, etc., so as to make the sound insulation layer less likely to vibrate.
Yet, in the conventional soundproof covers, it has been difficult to securely inhibit the sound insulation layers from vibrating so that the sound insulation layers themselves do not make a noise source in a case where the noise source vibrates considerably. Moreover, when the conventional soundproof covers are fastened to the noise source by way of a vibration insulation component member, such as a rubber mount, a grommet, etc., the number of the component parts increases by the number of the vibration insulation component members and simultaneously the man-hour requirement for the assembly enlarges. Accordingly, there arises a problem in that the manufacturing cost goes up.
In addition, in a case where the conventional soundproof covers are fastened by way of a vibration insulation component member, it has been required to provide a space which occupies by the height of the vibration insulation component member or more. Consequently, there arises a problem in that the assembly workability is impaired.
The present invention has been developed in view of such circumstances. It is therefore an object of the present invention to provide a soundproof cover which can be manufactured at a reduced cost and can get rid of the extra space being required in the assembly, and simultaneously which can inhibit a sound insulation layer itself from making a noise source.
A soundproof cover according to the present invention can solve the aforementioned problems, and comprises: a sealing layer having a peripheral portion, to be disposed so as to contact at least the peripheral portion with a noise source, and exhibiting elasticity; a sound insulation layer being formed as a hard plate shape, having an installation portion to be fastened to the noise source, and being disposed so as to cover the sealing layer; and a vibration inhibition layer disposed on at least a part of an interface between the sealing layer and the sound insulation layer so as to adhere to the sound insulation layer, and inhibiting the sound insulation layer from vibrating.
It is preferred that the sealing layer can be formed of polyurethane foam and can have a bonding portion, at which the sealing layer and the sound insulation layer are bonded, at an outer peripheral end thereof.
The sealing layer can desirably exhibit such a characteristic that a compression hardness falls in a range of from 100 to 1,000 N/314 cm2 (i.e., from 3.185xc3x97103 to 3.185xc3x97104 N/m2 approximately). Moreover, the vibration inhibition layer can desirably exhibit such characteristics that a static shear elastic modulus falls in a range of from 4 to 20 kgf/cm2 (i.e., from 3.923xc3x97105 to 1.961xc3x97106 N/m2 approximately) and a loss factor falls in a range of 0.03 or more.
Namely, in accordance with the present soundproof cover, it is possible not only to obviate a rubber mount, a grommet, etc., but also to inhibit the sound insulation layer itself from making a noise source. Therefore, it is possible to sharply reduce the number of component parts in the assembly as well as the man-hour requirement therefor. Thus, it is possible to manufacture the present soundproof cover at a less expensive cost.